This invention relates to a vehicle having a steering mechanism for enabling the vehicle to follow a guidance wire, such as a metallic wire or an optical wire, or fiber embedded in or applied to the surface of a vehicle supporting floor. The invention also relates to a method for guiding such a vehicle by means of such a guidance wire.
Automatically guided vehicles are used more and more often in both industrial and commercial operations. Vehicles of the type referred to in this application most commonly follow a wire embedded in or applied to the surface on which the vehicle moves. Guidance is by means of sensing devices that are typically placed on the undercarriage of the vehicle which sense the presence of the guidance wire and control the movement of the vehicle relative to the wire in response to programmed instructions. Such vehicles are used in warehousing operations to "pick" and deliver stock or inventory. Such vehicles also have application in assembly plants where items in the process of manufacture are delivered to successive stations by the vehicles.
A continuing problem in the development and use of automatically guided vehicles is the relative inability of such vehicles to maneuver accurately in tight spaces--particularly close right angle turns and the like. Recent developments include the device shown in the Krieg Patent, U.S. Pat. No. 3,912,037. This patent discloses an automobile assembly vehicle transport. The transport is controlled by antennas connected to and pivotally movable with driving wheels, one of which is a master and one of which is a slave. In one configuration, the wheels of the vehicles are substantially parallel to the longitudinal extent of the vehicle. However. when desired, the wheels can be turned perpendicular to the longitudinal width of the vehicle with the speed of at least one of the wheels being varied relative to the other wheel to permit movement of the vehicle by differential drive. Such a configuration presents a number of drawbacks. First, calibration of the movable antennas is critical. Secondly, the necessity for the antennas to be movable with the wheels limits substantially the variety of configurations which vehicles using this type of drive means can assume.